Linear actuator for endoscope, optical unit for endoscope, and endoscope

Abstract

A linear actuator for endoscope includes: a movable frame made of a magnetic material; a fixed frame in which the movable frame is provided so as to be movable forward and backward, the fixed frame being made of a non-magnetic material; two coils formed by being wound on an outer surface of the fixed frame, the two coils being disposed side by side in a longitudinal axis direction; a permanent magnet disposed in a manner stacked and superimposed on the two coils; and two yokes respectively disposed at a front and a back of the permanent magnet and the two coils.

What is claimed is: 
     
         1 . A linear actuator for endoscope, the linear actuator comprising:
 a movable frame made of a magnetic material, the movable frame holding a lens;   a fixed frame in which the movable frame is provided so as to be movable forward and backward, the fixed frame being made of a non-magnetic material;   two coils formed by being wound on an outer surface of the fixed frame, the two coils being disposed side by side in a longitudinal axis direction;   a permanent magnet disposed in a manner stacked and superimposed on the two coils; and   two yokes respectively disposed at a front and a back of the permanent magnet and the two coils.   
     
     
         2 . The linear actuator for endoscope according to  claim 1 , wherein the movable frame holds a movable lens that configures an optical system. 
     
     
         3 . The linear actuator for endoscope according to  claim 1 , wherein the two coils are wound on the fixed frame so as to have a same winding direction, and provided in different circuits to which current is supplied independently. 
     
     
         4 . The linear actuator for endoscope according to  claim 1 , wherein the two coils are wound on the fixed frame so as to have winding directions opposite to each other, and provided in a serial circuit. 
     
     
         5 . The linear actuator for endoscope according to  claim 1 , wherein the permanent magnet has a cylindrical shape and is disposed so as to cover entire circumferences of the two coils. 
     
     
         6 . The linear actuator for endoscope according to  claim 1 ,
 wherein the permanent magnet comprises two permanent magnets,   wherein the two permanent magnets are disposed at positions symmetrical to an optical axis of the lens.   
     
     
         7 . An optical unit for endoscope comprising:
 the linear actuator for endoscope according to  claim 1 .   
     
     
         8 . An endoscope comprising:
 an insertion portion including a distal end portion in which the optical unit for endoscope according to  claim 7  is disposed.